linux-kernel - Re: [PATCH v4 10/13] drm: zynqmp_dp: Use AUX IRQs instead of polling

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Message-ID: <911a0692-b1cd-4a97-9a99-2102d7f6f5ee@ideasonboard.com>
Date: Wed, 24 Apr 2024 15:30:50 +0300
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Sean Anderson <sean.anderson@...ux.dev>
Cc: Daniel Vetter <daniel@...ll.ch>, linux-arm-kernel@...ts.infradead.org,
 Michal Simek <michal.simek@....com>, linux-kernel@...r.kernel.org,
 David Airlie <airlied@...il.com>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v4 10/13] drm: zynqmp_dp: Use AUX IRQs instead of polling

On 23/04/2024 20:18, Sean Anderson wrote:
> Instead of polling the status register for the AUX status, just enable
> the IRQs and signal a completion.
> 
> Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
> ---
> 

This one seems to cause a hang when I unload the modules. I didn't debug 
it further yet, but most likely we get an AUX interrupt when disabling 
the hardware, and the driver hasn't disabled the IRQ handler.

  Tomi

> (no changes since v3)
> 
> Changes in v3:
> - New
> 
>   drivers/gpu/drm/xlnx/zynqmp_dp.c | 35 +++++++++++++++++++++++---------
>   1 file changed, 25 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> index 9d61b6b8f2d4..863668642190 100644
> --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> @@ -285,6 +285,7 @@ struct zynqmp_dp_config {
>    * @next_bridge: The downstream bridge
>    * @config: IP core configuration from DTS
>    * @aux: aux channel
> + * @aux_done: Completed when we get an AUX reply or timeout
>    * @phy: PHY handles for DP lanes
>    * @num_lanes: number of enabled phy lanes
>    * @hpd_work: hot plug detection worker
> @@ -305,6 +306,7 @@ struct zynqmp_dp {
>   	struct drm_bridge bridge;
>   	struct work_struct hpd_work;
>   	struct work_struct hpd_irq_work;
> +	struct completion aux_done;
>   	struct mutex lock;
>   
>   	struct drm_bridge *next_bridge;
> @@ -941,12 +943,15 @@ static int zynqmp_dp_aux_cmd_submit(struct zynqmp_dp *dp, u32 cmd, u16 addr,
>   				    u8 *buf, u8 bytes, u8 *reply)
>   {
>   	bool is_read = (cmd & AUX_READ_BIT) ? true : false;
> +	unsigned long time_left;
>   	u32 reg, i;
>   
>   	reg = zynqmp_dp_read(dp, ZYNQMP_DP_INTERRUPT_SIGNAL_STATE);
>   	if (reg & ZYNQMP_DP_INTERRUPT_SIGNAL_STATE_REQUEST)
>   		return -EBUSY;
>   
> +	reinit_completion(&dp->aux_done);
> +
>   	zynqmp_dp_write(dp, ZYNQMP_DP_AUX_ADDRESS, addr);
>   	if (!is_read)
>   		for (i = 0; i < bytes; i++)
> @@ -961,17 +966,14 @@ static int zynqmp_dp_aux_cmd_submit(struct zynqmp_dp *dp, u32 cmd, u16 addr,
>   	zynqmp_dp_write(dp, ZYNQMP_DP_AUX_COMMAND, reg);
>   
>   	/* Wait for reply to be delivered upto 2ms */
> -	for (i = 0; ; i++) {
> -		reg = zynqmp_dp_read(dp, ZYNQMP_DP_INTERRUPT_SIGNAL_STATE);
> -		if (reg & ZYNQMP_DP_INTERRUPT_SIGNAL_STATE_REPLY)
> -			break;
> +	time_left = wait_for_completion_timeout(&dp->aux_done,
> +						msecs_to_jiffies(2));
> +	if (!time_left)
> +		return -ETIMEDOUT;
>   
> -		if (reg & ZYNQMP_DP_INTERRUPT_SIGNAL_STATE_REPLY_TIMEOUT ||
> -		    i == 2)
> -			return -ETIMEDOUT;
> -
> -		usleep_range(1000, 1100);
> -	}
> +	reg = zynqmp_dp_read(dp, ZYNQMP_DP_INTERRUPT_SIGNAL_STATE);
> +	if (reg & ZYNQMP_DP_INTERRUPT_SIGNAL_STATE_REPLY_TIMEOUT)
> +		return -ETIMEDOUT;
>   
>   	reg = zynqmp_dp_read(dp, ZYNQMP_DP_AUX_REPLY_CODE);
>   	if (reply)
> @@ -1055,6 +1057,9 @@ static int zynqmp_dp_aux_init(struct zynqmp_dp *dp)
>   			(w << ZYNQMP_DP_AUX_CLK_DIVIDER_AUX_FILTER_SHIFT) |
>   			(rate / (1000 * 1000)));
>   
> +	zynqmp_dp_write(dp, ZYNQMP_DP_INT_EN, ZYNQMP_DP_INT_REPLY_RECEIVED |
> +					      ZYNQMP_DP_INT_REPLY_TIMEOUT);
> +
>   	dp->aux.name = "ZynqMP DP AUX";
>   	dp->aux.dev = dp->dev;
>   	dp->aux.drm_dev = dp->bridge.dev;
> @@ -1072,6 +1077,9 @@ static int zynqmp_dp_aux_init(struct zynqmp_dp *dp)
>   static void zynqmp_dp_aux_cleanup(struct zynqmp_dp *dp)
>   {
>   	drm_dp_aux_unregister(&dp->aux);
> +
> +	zynqmp_dp_write(dp, ZYNQMP_DP_INT_DS, ZYNQMP_DP_INT_REPLY_RECEIVED |
> +					      ZYNQMP_DP_INT_REPLY_TIMEOUT);
>   }
>   
>   /* -----------------------------------------------------------------------------
> @@ -1685,6 +1693,12 @@ static irqreturn_t zynqmp_dp_irq_handler(int irq, void *data)
>   	if (status & ZYNQMP_DP_INT_HPD_IRQ)
>   		schedule_work(&dp->hpd_irq_work);
>   
> +	if (status & ZYNQMP_DP_INTERRUPT_SIGNAL_STATE_REPLY)
> +		complete(&dp->aux_done);
> +
> +	if (status & ZYNQMP_DP_INTERRUPT_SIGNAL_STATE_REPLY_TIMEOUT)
> +		complete(&dp->aux_done);
> +
>   	return IRQ_HANDLED;
>   }
>   
> @@ -1708,6 +1722,7 @@ int zynqmp_dp_probe(struct zynqmp_dpsub *dpsub)
>   	dp->dpsub = dpsub;
>   	dp->status = connector_status_disconnected;
>   	mutex_init(&dp->lock);
> +	init_completion(&dp->aux_done);
>   
>   	INIT_WORK(&dp->hpd_work, zynqmp_dp_hpd_work_func);
>   	INIT_WORK(&dp->hpd_irq_work, zynqmp_dp_hpd_irq_work_func);